The risk of disease transmission resulting from the incorrect use or disposal of syringes is a serious problem around the world.
Diseases such as HIV (Human Immuno-deficiency Virus) and Hepatitis B along with other blood borne diseases are readily transmitted between persons when a contaminated needle tip comes into contact with and penetrates the skin of a third party.
Protocols exist in hospitals and medical facilities which dictate that a used syringe must be disposed of in a sharps waste unit immediately after an injection has been given. However, the risk still exists of a medical practitioner or other person being injured by the needle tip in a needle stick injury during the disposal of the syringe.
The problem of correct syringe disposal is particularly prevalent amongst intravenous drug users who commonly dispose of syringes without paying head to standard disposal protocols. The discarding of syringes in public places puts the population at risk of needle stick injuries.
The spread of blood borne diseases through the re-use of syringes is a significant problem amongst intravenous drug users. When a needle is refilled after an injection and subsequently injected by another person without adequate sterilisation, there is a serious risk of any diseases carried by the first person being transmitted to the second person.
A retractable syringe has been proposed in which a metallic clip is affixed to the head of the syringe plunger. As the plunger is pushed within the barrel during an injection stroke, the metallic clip frictionally engages with an internal wall of a needle hub, causing the head of the plunger to lock within the needle hub. A subsequent withdrawal of the plunger causes the needle hub, and the needle tip to retract within the body of the barrel, preventing a user or other person from accidentally coming into contact with the needle tip.
However, a problem associated with such retractable syringes is that they are typically more expensive to manufacture than conventional, non-retractable syringes. A further problem is that the metallic clip is known to occasionally not adequately engage with the needle hub. Accordingly, the retractability of the syringe may not operate in all syringes from a given batch. Clearly this is unfavourable in medical applications where syringe malfunction is not acceptable and places the user at risk.